Controller for electronic power steering apparatus

Abstract

A controller of an electrically driven power steering apparatus that can be realized by using a low-cost structure to perform a fault diagnosis of A / D converters and that can determine a fault part, for example, which one of the A / D converters is in a fault state to determine whether the application of a steering assist force should be stopped or continued, with the result that the fault diagnosis places no excessive load on a main MCU. A main MCU with an A / D converter (1), a sub MCU with an A / D converter (2), and a D / A converter are provided. The sub MCU outputs a predetermined value to a D / A converter. An error between a predetermined value and a return value (1) obtained by transmitting a predetermined value to the sub MCU through a D / A converter and A / D converter (1) are compared in the sub MCU. An error between a predetermined value and a return value (2) obtained by transmitting a predetermined value to the sub MCU through a D / A converter and A / D converter (2) are compared in the sub MCU to perform the fault diagnosis.

Description

TECHNICAL FIELD [0001] The present invention relates to a controller for an electric power steering apparatus, and more particularly to a controller for an electric power steering apparatus wherein the controller can perform a fault diagnosis of an A / D converter and a D / A converter, which are used in the controller. Background Technique [0002] An electric power steering apparatus, which urges a steering apparatus of an automobile or a vehicle by means of a rotational force of a motor, imparts a driving force of the motor to a steering shaft or a rack axis through a transmission mechanism such as gears or a belt through reduction gears. Such a conventional electric power steering apparatus carries out a feedback control of a motor current in order to accurately generate an assist torque (a steering assist torque). The feedback control is to adjust a motor applied voltage to reduce the difference between a current command value and a motor current detection value. The motor applied vo...

AI Technical Summary

Problems solved by technology

Since the electric power steering apparatus that performs the fault diagnosis as described in the Patent Reference 1 mentioned above employs a system of dual controllers each comprising a CPU and the like, it involves a problem that the cost of the apparatus increases.

Furthermore, another problem lies in that it is impossible to identify a fault part, i.e., to identify which an A / D converter, which a D / A converter, or which a steering sensor is faulty.

In addition, there is another problem that when the main CPU or any port of the A / D converter associated with the main CPU is used for such the fault diagnosis, the fault diagnosis places excessive load on the main CPU or the A / D converter associated with the main CPU, which adversely affects a proper control by the electric power steering apparatus.

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